In order to process a semiconductor device, a plurality of process steps must be performed. At each of these process steps, there is typically a “masking” step wherein certain portions of the substrate are masked off from the process, i.e., the process being performed is inhibited from acting upon that certain area. For example, during an implant step, there are only certain areas of substrate that are to be subjected to the implant of impurities therein. It is important to prevent other areas from being implanted with these impurities. This masking step utilizes a photo resist etching procedure wherein the photo resist is first deposited on the surface of the substrate and then exposed through the mask and then etched such that the unexposed portions of the photo resist are removed to expose certain areas of the substrate for processing.
When the masks are defined, they are defined with a set of data that consists of the various processes that are involved at particular stages in the process. For example, it may be that a particular integrated circuit has a flash memory associated therewith which is subject to a “flash implant process.” During this flash process, there may be a p-implant that is performed. The data will indicate that the area to be processed will result in a p-type area being implanted during a flash process, which p-implant for the flash process may be different than a p-implant for a standard device. If the p-type implant were to be performed during a non-flash implant process, it would be important that the data indicate that a p-type implant be performed and that it is to be performed during the flash process. The database is created such that the physical layout of the mask is provided and also information as to when that layout should be processed, wherein there are a plurality of separate physical layouts associated with a given mask, each created as a separate operation. This data is typically provided in a GDSII format that is provided to the manufacturer in the form of the layers that must be combined to form a mask, and the manufacturer converts this from that format to their own format and then manufactures the mask in accordance with that format. However, if the manufacturer made a mistake and did not convert the data correctly, it might be that the p-type implant were made into a particular area during a non-flash process when it should have been made during a flash process, this possibly resulting in a different implant level. This is due to the fact that the manufacturer must ensure that all of the correct physical layout layers are combined correctly in the mask.
There are also two types of conversion operations that need the attention of the manufacturer, that of a clear tone mask and a dark tone mask. For some reasons, a structure is defined wherein the actual data indicates an area that is to remain on the substrate after processing whereas another process provides a structure that results in material being removed in accordance with the structure. During manufacturing, the data is first converted, the mask is inverted and then a mask layout generated from the data. For example, a metal strip will have data generated indicating a strip of metal as the pattern. The data for this structure must be converted to a mask wherein the material for that structure will remain, i.e., the photo resist around that area is removed and that area outside of the structure etched. This will require the mask to have that area (of the metal strip) as the clear area of the mask so that the photo resist will be exposed over the area that will correspond to the structure. When the mask is made though, the area associated with the structure is dark—not transparent. This is a dark tone mask which, by the process that it is used, results in a negative image. If the manufacturer fails to do this, the results will not be acceptable. For a clear tone mask, there is no inversion required, as the structure that is the subject of the mask is laid out in the physical layout as it would appear in the mask. For example, if a via is to be formed, the physical layout will have a solid area indicating the via, but the mask must have a “hole” in that area and, therefore, must not be inverted to indicate such.